Private/Get-NinjaOneToken.ps1

function Get-NinjaOneToken {
    [CmdletBinding()]
    param()

    if ($Script:NinjaOneInstance -and $Script:NinjaOneClientID -and $Script:NinjaOneClientSecret ) {
        if ($Script:NinjaTokenExpiry -and (Get-Date) -lt $Script:NinjaTokenExpiry) {
            return $Script:NinjaToken
        } else {

            if ($Script:NinjaOneRefreshToken) {
                $Body = @{
                    'grant_type'    = 'refresh_token'
                    'client_id'     = $Script:NinjaOneClientID
                    'client_secret' = $Script:NinjaOneClientSecret
                    'refresh_token' = $Script:NinjaOneRefreshToken
                }
            } else {

                $body = @{
                    grant_type    = 'client_credentials'
                    client_id     = $Script:NinjaOneClientID
                    client_secret = $Script:NinjaOneClientSecret
                    scope         = 'monitoring management'
                }
            }

            $token = Invoke-RestMethod -Uri "https://$($Script:NinjaOneInstance -replace '/ws','')/ws/oauth/token" -Method Post -Body $body -ContentType 'application/x-www-form-urlencoded' -UseBasicParsing
    
            $Script:NinjaTokenExpiry = (Get-Date).AddSeconds($Token.expires_in)
            $Script:NinjaToken = $token
            

            Write-Host 'Fetched New Token'
            return $token
        } else {
            Throw 'Please run Connect-NinjaOne first'
        }
    }

}